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Summer Skin Trouble Survey: 67.3% of Those Who Experienced Heat Rash Couldn't Distinguish It from Sweat Rash, Only 23.7% Knew the Difference from Metal Allergy

Published Jul 6, 2026 6:00 PM ・ Updated Jul 8, 2026 6:03 PM ・ 38 min read ・ Source: PR TIMES

【Conclusion】Key Points of This Survey To summarize, there are primarily three causes for itchy skin due to sweat, and each requires a different approach. Heat rash (miliaria) is a rash caused by bloc

【Conclusion】Key Points of This Survey

To summarize, there are primarily three causes for itchy skin due to sweat, and each requires a different approach. Heat rash (miliaria) is a rash caused by blocked sweat ducts. Sweat rash (sweat-induced eczema) is contact dermatitis caused by the components of sweat. Metal allergy is an allergic reaction to metal ions dissolved by sweat. It is important to differentiate based on the affected area and progression to ensure appropriate treatment.

- 67.3% of those who experienced skin trouble due to sweat responded that they "could not distinguish between heat rash and sweat rash."

- 42.0% have experienced skin irritation from accessories in the summer, and of those, 58.7% suspected a metal allergy.

- 78.3% of those who visited a dermatologist for sweat-related troubles responded, "I wish I had visited sooner."

Glossary

What is Heat Rash (Miliaria)?

Heat rash, medically known as "miliaria," is a skin condition that occurs when the openings of sweat glands (eccrine glands) become blocked, causing sweat to accumulate within the skin and lead to inflammation. It typically appears as small red bumps or blisters. It commonly occurs in areas where sweat tends to accumulate, such as the neck, inner elbows, and behind the knees.

What is Sweat Rash (Sweat-Induced Eczema)?

Sweat rash is a type of contact dermatitis caused by the irritation of the skin by components in sweat, such as salt and ammonia. While heat rash is caused by blocked sweat ducts, sweat rash is a reactive response on the skin's surface, characterized by widespread redness, itching, and a stinging sensation.

What is Metal Allergy (Contact Dermatitis)?

Metal allergy is an allergic contact dermatitis where metal ions, dissolved by sweat or other moisture, bind with skin proteins, triggering an immune response. Nickel, cobalt, and chromium are considered the three main causative metals. Symptoms are typically localized to the areas that have come into contact with accessories or watches.

Comparison Table: Heat Rash, Sweat Rash, and Metal Allergy

Comparison Item

Heat Rash (Miliaria)

Sweat Rash

Metal Allergy

Cause

Blockage of sweat ducts

Irritation from sweat components

Allergic reaction to metal ions

Symptom Characteristics

Small red bumps/blisters

Widespread redness/itching

Redness, swelling, blisters at contact site

Common Sites

Areas where sweat accumulates (neck, elbows, behind knees, etc.)

Large areas where sweat is present

Only at accessory contact sites

Severity of Itching

Mild to moderate

Moderate to severe

Severe

Time to Onset

Several hours to 1 day

Immediately after sweating to several hours

24 to 72 hours after contact

Spontaneous Healing

Improves in a few days with cooling

Tends to improve with washing off sweat

Persists if cause is not removed

*These are general guidelines and individual differences may apply.

IC Clinic (Shinjuku, Shibuya, Ueno, Ikebukuro, Tokyo, Omiya branches), operated by Medical Corporation Tetsukenkai, conducted an "Awareness Survey on Skin Troubles Caused by Summer Sweat" targeting 300 men and women aged 20-60 nationwide, as the Tanabata season approaches and interest in summer sweat troubles rises. This survey clarifies the differences between "heat rash," "sweat rash," and "metal allergy," which are often confused, and the level of awareness regarding appropriate treatment methods.

Survey Background

During the summer, with rising temperatures and humidity, the number of patients complaining of skin troubles due to sweat increases sharply. July, in particular, is a time when opportunities to wear accessories increase, such as for outings in yukata and summer festivals. Dermatologists often receive consultations like "my neck became itchy from my necklace" or "my earlobes turned red from earrings." However, currently, few people can correctly distinguish whether these symptoms are heat rash, sweat rash, or metal allergy. Since there are cases where symptoms are worsened by incorrect self-treatment, this survey aims to promote correct knowledge.

Survey Overview

Survey Target: Men and women aged 20-60 nationwide who have experienced skin troubles due to sweat in the summer.

Survey Period: June 15-24, 2026

Survey Method: Internet survey

Number of Respondents: 300

Survey Results

【Survey Results】The most common sweat-related trouble is "itching" at 82.3%, followed by "redness/rash" at 71.7%

Question: Please select all sweat-related skin troubles you have experienced in the summer (multiple answers allowed).

"Itching" is the most common sweat-related skin trouble, experienced by over 80% of respondents. Since itching is a common symptom across heat rash, sweat rash, and metal allergy, it suggests that identifying the cause based on symptoms alone is difficult.

【Survey Results】67.3% responded they "could not distinguish" between heat rash and sweat rash.

Question: Do you know the difference between heat rash (miliaria) and sweat rash (sweat-induced eczema)?

It was revealed that approximately 70% of people cannot recognize the difference between heat rash and sweat rash. Since both have different causes and treatment methods, having correct knowledge leads to appropriate care.

【Survey Results】42.0% experienced skin irritation from wearing accessories in the summer, and nearly 60% of them suspected metal allergy.

Question: Have you ever experienced skin irritation from wearing accessories (necklaces, earrings, bracelets, watches, etc.) in the summer?

Over 40% of people have experienced skin irritation from wearing accessories in the summer, and caution is especially needed during this period when events like Tanabata and summer festivals increase. When you sweat, metal ions are more likely to dissolve, making metal allergy symptoms more likely to appear in the summer.

【Survey Results】78.3% of those who visited a dermatologist responded, "I wish I had visited sooner."

Question: Have you ever visited a dermatologist for sweat-related skin troubles?

While about 80% of those who have visited feel the importance of early consultation, over 60% are treating it with over-the-counter medications or neglecting it. If symptoms persist or worsen, it is recommended to consult a dermatologist without self-diagnosing.

【Survey Results】52.7% do not know about the existence of metal allergy testing, and only 11.0% have undergone testing.

Question: Do you know that there is a test (patch test) to determine if you have a metal allergy?

It was found that over half of respondents are unaware of the patch test, which is effective for the definitive diagnosis of metal allergy. For those who repeatedly experience skin irritation from accessories, identifying the causative metal can lead to appropriate prevention.

Survey Summary

This survey revealed the current situation where many people lack correct knowledge about skin troubles caused by summer sweat. In particular, only about 30% understand the difference between heat rash and sweat rash, and over half do not know that there are tests for metal allergy. On the other hand, about 80% of those who have visited a dermatologist feel the importance of early consultation, highlighting the significance of receiving proper diagnosis and treatment. Ahead of the summer event season, it is important to understand the differences between these three sweat-related troubles and take appropriate action according to the symptoms.

Doctor's Comment | Dr. Kota Takakuwa, IC Clinic

Based on over 15 years of clinical experience as a dermatologist, the symptoms of patients who come to the clinic complaining of "itchy skin due to sweat" in the summer can be broadly categorized into three: heat rash, sweat rash, and metal allergy, each with different causes and treatments. Knowing how to distinguish them correctly is the first step toward proper care.

Heat rash (miliaria) occurs when the openings of sweat glands become blocked due to heavy sweating, causing sweat to accumulate within the skin. It appears as small red bumps or clear blisters in areas where sweat accumulates, such as the neck, inner elbows, and behind the knees. It often improves within a few days with a cool environment and keeping the skin clean.

On the other hand, sweat rash (sweat-induced eczema) is contact dermatitis caused by the irritation of the skin by components in sweat, such as salt and ammonia. After sweating, it causes widespread redness, itching, and a stinging sensation. Unlike heat rash, it is a surface irritation reaction rather than a blockage of sweat ducts, so frequently wiping or washing off sweat can help prevent it.

Metal allergy is an immune response triggered by metal ions dissolved by sweat binding with skin proteins. Symptoms are typically localized to the areas in contact with accessories like necklaces and earrings, and symptoms often appear 24 to 72 hours after contact. In summer, sweat makes metals dissolve more easily, so even accessories that are normally fine can cause symptoms.

The Guidelines for Management of Contact Dermatitis by the Japanese Dermatological Association also state that identifying and avoiding the causative agent is the basis of treatment. For those suffering from recurrent symptoms, we recommend identifying the cause through a patch test.

【Evidence】The Guidelines of the Japanese Dermatological Association indicate that patch testing is useful in diagnosing contact dermatitis and that identifying the causative agent allows for effective prevention.

How to Differentiate the Three Sweat-Related Troubles

- Heat Rash: Small scattered rashes in areas where sweat accumulates; improves with cooling. - Sweat Rash: Widespread redness and stinging sensation where sweat is present; relieved by washing off sweat. - Metal Allergy: Localized only to the area of accessory contact; symptoms persist for 24-48 hours even after removal.

Precautions When Wearing Accessories in Summer

- Wipe off sweat frequently or temporarily remove accessories. - Applying a coating agent to areas that come into direct contact with the skin is also an option. - For those prone to symptoms, choose materials such as titanium or surgical stainless steel.

Symptoms Recommended for Dermatologist Consultation

- If symptoms do not improve after using over-the-counter remedies for more than a week. - If the symptoms are spreading or blisters are weeping or spreading. - If redness or swelling is observed along the shape of accessories. - If the same symptoms recur every summer.

Clinic Information

Features of IC Clinic

- Doctors with specialized knowledge in dermatology and plastic surgery are available for accurate diagnosis of heat rash, sweat rash, and metal allergy. - We offer a wide range of treatments, from prescribing topical and oral medications according to symptoms to approaches for severe cases. - Six branches (Shinjuku, Shibuya, Ueno, Ikebukuro, Tokyo, Omiya) offer weekend consultations, making it convenient for visits after work or on holidays. - We can also identify the cause of metal allergies through patch testing.

IC Clinic Shinjuku Branch: Imazu Aoi Bldg. 2F, 2-5-3 Yoyogi, Shibuya-ku, Tokyo

IC Clinic Shibuya Branch: New Sansui Bldg. 5F, 3-16-2 Shibuya, Shibuya-ku, Tokyo

IC Clinic Ueno Branch: Sankyu Bldg. 1F, 3-16-5 Higashi-Ueno, Taito-ku, Tokyo

IC Clinic Ikebukuro Branch: Maeda Bldg. 9F, 2-15-3 Minami-Ikebukuro, Toshima-ku, Tokyo

IC Clinic Tokyo Branch: Nihonbashi Front 3F, 3-6-2 Nihonbashi, Chuo-ku, Tokyo

IC Clinic Omiya Branch: Fukubi Medical 2F, Unit B, 1-60 Daimoncho, Omiya-ku, Saitama City, Saitama

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Frequently Asked Questions (Q&A)

Q1. Is itchy skin due to sweat a metal allergy?

A. Itchy skin due to sweat can be caused by heat rash, sweat rash, or metal allergy, and can be distinguished by the location and progression of the symptoms.

This survey found that 82.3% of those with sweat troubles complained of itching, indicating that it is difficult to determine the cause based on itching alone. In the case of metal allergy, symptoms are typically localized to the area of contact with accessories. If the itching is widespread, heat rash or sweat rash is more likely. If symptoms recur, we recommend diagnosis at a dermatology clinic.

Q2. What is the difference between sweat rash and heat rash?

A. Heat rash is a rash caused by blocked sweat ducts, while sweat rash is caused by skin irritation from sweat components, and the onset mechanisms are different.

Survey results showed that 67.3% of respondents were unaware of this difference. Heat rash causes small rashes and blisters due to blocked sweat ducts and is localized to areas where sweat accumulates, such as the neck and behind the elbows. Sweat rash is caused by the irritation of the skin by components like salt in sweat, resulting in redness over a wide area where sweat is present. The treatment methods also differ: heat rash is treated by cooling to suppress sweat, while sweat rash is primarily managed by frequently washing off sweat.

Q3. What causes itching on the neck from a necklace?

A. The cause of itching on the neck from a necklace in the summer is likely a metal allergy due to metal ions dissolved by sweat.

In this survey, 42.0% experienced skin irritation from accessories, and in the summer, sweat makes metals more likely to dissolve. It is often caused by accessories containing nickel or cobalt, and redness typically appears along the shape of the necklace. Symptoms often appear 24 to 72 hours after contact, so symptoms may appear the day after removal. Identifying the causative metal through a patch test allows for appropriate material selection.

Q4. Is there a way to check if I have a metal allergy?

A. You can accurately check which metals you are allergic to by undergoing a patch test at a dermatology clinic.

The survey revealed that 52.7% of respondents were unaware of the existence of patch testing. A patch test involves applying various metal reagents to the skin and checking for reactions after 48 and 72 hours. Multiple metals, such as nickel, cobalt, and chromium, can be tested simultaneously, and identifying the causative metal clarifies which accessories or dental metals to avoid. Although only 11.0% have undergone the test, it is recommended for those with recurrent symptoms.

Q5. How can I prevent summer sweat-related troubles?

A. The basics are to frequently wipe or wash off sweat, wear breathable clothing, and pay attention to materials if you have a metal allergy.

The survey indicated that 37.3% of respondents treat their condition with over-the-counter medications, but the basic principle of prevention is not to let sweat remain on the skin for extended periods. Wear absorbent underwear and take a shower or wipe off sweat with a damp towel frequently. When wearing accessories, it is effective to remove them during activities that cause sweating or choose materials that are less likely to cause allergies, such as titanium or surgical stainless steel. If symptoms still occur, as 78.3% of those who have visited a clinic feel the importance of early consultation, we recommend consulting a dermatologist.

Risks of Neglect

- If sweat rash is left untreated, bacterial infections (impetigo) can occur due to scratching. - If metal allergy is left untreated, sensitization may progress, and reactions may spread to other metals. - Repeated heat rash can leave behind pigmentation marks.

Consultation Recommended For:

- If symptoms do not improve after using over-the-counter anti-itch medication for one week. - If symptoms are spreading or blisters are weeping or spreading. - If redness or swelling is observed along the shape of accessories. - If the same symptoms recur every summer.